In known devices of this type, it is conventional for the cutter bar, which extends parallel to the axis of the roll, to be resiliently urged against the periphery of the roll and to ride thereon. The cutter bar is normally shaped transversely thereof so as to bear on the roll both at its leading, or cutting, edge and adjacent its trailing edge.
Such prior devices are widely used for cutting nonelectrically conductive materials such as paper, plastic film and the like, which are typically wound on cardboard cores. In such prior devices, the sheet material has been found to have a tendency to bunch up behind the cutting blade, as the roll is rotatably advanced by hand for exposing a previously cut edge of the sheet material preparatory to cutting a fresh piece therefrom. It is believed this may be caused by development of a static electrical charge on the sheet material as it is being wound on or unwound from the roll. Also, in such prior devices, the free end portion of the sheet material on the roll has tended to snap back against the periphery of the roll, creating difficulty in dislodging it preparatory to drawing a fresh length of material from the roll. It is believed that this "snap-back" is due to generation of a static electric charge during the unrolling of the sheet material while it is in substantial surface contact with the cutting blade, particularly with the trailing edge thereof.